Need Help Getting a WR400 Running Again


13 replies to this topic
  • hattackk

Posted December 19, 2014 - 10:53 PM

#1

Hey Guys,

 

Here is a little back story on the bike. I was given this bike a while back and it didn't run (shocker). I did all the normal checks when evaluating the reason why it wasn't starting ie spark,fuel,compression,air. The bike was getting spark had plenty of compression. I decided to go ahead and rebuild the carb. During the tear down obviously the jets were a little clogged and the accelerator pump diaphragm was trashed. I replaced everything with brand new parts and cleaned out all of the jets. I then checked the float height and adjusted accordingly. I put the bike back together with the fresh carb and new petcock. I followed the starting procedure I found on this forum with no success. I decided to try starting fluid, still with no success. I once again verified the bike was getting fuel and spark, which it was. I checked the timing and it was correct (exhaust cam was rotated clockwise 1 tooth which I found is a yz timing adjustment). The bike has plenty of compression but still won't start. I'm starting to run out of ideas at this point :banghead: . Any suggestions would be greatly appreciated! The bike is a 99 WR400F with stock jetting and stock exhaust.



  • hattackk

Posted December 19, 2014 - 11:37 PM

#2

I will be doing valve clearance checks tomorrow.



  • Birdy426

Posted December 20, 2014 - 12:58 AM

#3

Are you following the starting drill?  Also, check all the vacuum lines for the hot start for cracks, and make sure the throttle slide in in properly (easy to put them in backwards)



  • hattackk

Posted December 20, 2014 - 07:55 AM

#4

The vacuum hoses for the hot-start look good, the one going to the airbox is disconnected, but I wouldn't think that would mater. I'm following the starting procedure to the T. Throttle cables are disconnected so no change of twisting the the throttle by accident.


Edited by hattackk, December 20, 2014 - 07:58 AM.


  • hattackk

Posted December 20, 2014 - 03:33 PM

#5

Here's an update. Checked valve clearances and everything is within spec. Put a new cr8eix sparkplug with a fresh tank of 93oct. The bike still won't fire.I'm out of thoughts at this point. Plug is wet so I know it is getting fuel and spark plug is sparking well.

Edited by hattackk, December 20, 2014 - 03:52 PM.


  • hattackk

Posted December 20, 2014 - 08:05 PM

#6

I found one of the wires to the kill switch cut. I would imagine if that was the issue I wouldn't be getting spark?

  • Birdy426

Posted December 20, 2014 - 09:27 PM

#7

yes, if the cut end was contacting ground you wouldn't  be getting spark (assuming it's the leg between the switch and the CDI not the leg between the switch and ground).  If the throttle cables are disconnected, you aren't following the Dubacj Method (the drill), which calls for a couple of twists of the throttle before you kick to squirt a bit of gas into the ports...



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  • hattackk

Posted December 20, 2014 - 10:55 PM

#8

It is getting plenty of spark, I was following the method that stated never to touch to thottle. I'll hook up the cables and try the Dubacj method.



  • Krannie McKranface

Posted December 21, 2014 - 07:18 AM

#9

If you are continually trying to start it, you are filling up the crankcase with un-burnt fuel.

You have to remove those gasses before it will start.

 

For every 5 attempts, you need to clear the cylinder by holding the throttle wide open, kill button held down, and kick it gingerly about a dozen  times.

 

It won't start till you do that.



  • hattackk

Posted December 22, 2014 - 08:38 PM

#10

The hot start was not connected on the bike when I got it. I'm looking at the service manual and it looks like there is a piece that mounts to the carb where the hotstart Ts into from the head. Can someone take a picture of how their hotstart is setup on a 99 WR400. Thanks!



  • hattackk

Posted December 22, 2014 - 09:39 PM

#11

So I was looking to replace the diaphragm assembly that bolts to the carb and hooks into the hot start but looks like the spring is obsolete and is no longer available, any suggestions? Could this be a reason for it not starting. If it is removed does something need to be plugged?



  • Krannie McKranface

Posted December 23, 2014 - 08:59 AM

#12

You have to have all openings plugged.

You can just push the piston down into the cavity, and use any spring to hold it down that fits, and even use no cable, if you want.



  • hattackk

Posted December 23, 2014 - 06:33 PM

#13

Okay so this bike has just been a bag full of mysteries. I was in the process of putting new jets in the carb and the pilot jet wasn't matching what came out of the carb. I was thinking maybe the guy was wrong about the year. I checked the Vin number and it has indicated it is actually a 1999 YZ400.

  • fdme

Posted December 29, 2014 - 09:40 AM

#14

Okay so this bike has just been a bag full of mysteries. I was in the process of putting new jets in the carb and the pilot jet wasn't matching what came out of the carb. I was thinking maybe the guy was wrong about the year. I checked the Vin number and it has indicated it is actually a 1999 YZ400.


Another wonderful reminder of the world of used bikes lol. I've had many of the same experiences with mine.

You could have a different model carb than you thought... It's always fun figuring this stuff out.




 
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